Why Do Sunspots Appear Dark?

Sunspots appear dark because they are cooler than the surrounding area. While sunspots are “cooler,” they are definitely still hot (4,000 °K); they are only cooler in comparison to the rest of the sun’s surface (5,778 °K).

Let’s take for example getting a metal rod and heating a part of it slightly, the spot would burn bright. Taking that same rod and heating a different part of it but even hotter, it would burn brighter than the one you previously heated, making the former appear darker than the latter. This is the same concept as sunspots. The higher temperature surrounding the sunspot makes it appear darker than it truly is.

Why Do Sunspots Appear?

Sunspots appear when the convective flow of the sun mixes in with concentrated magnetic fluxes by the photosphere. These fluxes create pressure, which subsequently causes the gasses to cool down and expand outwards into the corona.

The sun’s convective flow is a result of heat pushing outwards from the core. This flow produces energy. Additionally, the sun has its own magnetic field. Together, these two factors create sunspots.

Sunspots usually appear in pairs and last for a few days to weeks. As sunspots move across the surface of the sun, they sometimes disappear and reappear elsewhere. Sunspot activity varies over an 11-year cycle, with more sunspots appearing during peak activity.

The 11-Year Cycle

The 11-year cycle is merely an observational phenomenon of the sun. This was noted by astronomer Heinrich Schwabe, who observed that sunspot activity would go through cycles of peak and low activity.

The cause of the 11-year cycle is still not fully understood, but it is thought to be linked to the sun’s magnetic field.

Sunspots and Correlation to Earth

The sunspot cycle affects the Earth’s climate. However, scientists are still trying to figure out the science behind this.

It has been observed that during the 17th century when the sun went through a period of inactivity, the earth experienced a “Little Ice Age,” where rivers that usually don’t freeze froze over and snow was frequent.